This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Digital Light Processing (“DLP”) is a display technology that employs an optical semiconductor, known as a Digital Micromirror Device (“DMD”) to project video onto a screen. DMDs typically contain an array of at least one million or more microscopic mirrors mounted on microscopic hinges. Each of these mirrors is associated with a point on the screen, known as a pixel. By varying the amount of light that is reflected off each of these mirrors, it is possible to project video onto the screen. Specifically, by electrically actuating each of these hinge-mounted microscopic mirrors, it is possible to either illuminate a point on the screen (i.e., “turn on” a particular micromirror) or to leave that particular point dark by reflecting the light somewhere else besides the screen (i.e., “turn off” the micromirror). Further, by varying the amount of time a particular micromirror is turned on, it is possible to create a variety of gray shades. For example, if a micromirror is turned on for longer than it is turned off, the pixel that is associated with that particular micromirror will have a light gray color; whereas if a particular micromirror is turned off more frequently than it is turned on, that particular pixel will have a darker gray color. In this manner, video can be created by turning each micromirror on or off several thousand times per second. Moreover, by sequentially shining red, green, and blue at the micromirrors instead of white light, it is possible to generate millions of shades or color instead of shades of gray.
As stated above, the shading of a particular pixel may be partially determined by the length of time that the micromirror corresponding to that pixel is either turned on or turned off. This shading can be quantified using a measurement referred to as the least significant bit (“LSB”). For example, DMDs are typically configured to display 256 shades from off (0 LSBs) to all on (256 LSBs) with each shade between 0 and 255 becoming successively brighter. It is possible to create a variety of different color shades by combining various LSBs of red light, green light, and blue light (i.e., primary colors of light). For example, one color shade may be formed from 30 LSBs of red light, 150 LSBs of green light, and 85 LSBs of blue light, another shade from 212 LSBs of red light, 156 LSBs of green light, and 194 LSBs of blue light, and so forth. Because the three colors of light are shined sequentially and rapidly, a viewer sees a single shade of light formed from the three different colors of light.
One technique for generating the sequential stream of colored light is with a color wheel. A color wheel typically includes six color filters arrayed red, green, blue, red, green, blue around the circumference of a wheel. By shining white light at the circumference of the color wheel and rotating the color wheel, it is possible to generate a sequential stream of red, green, and blue light. However, the colored light may become briefly inconsistent when the colored light transitions between primary colors. Due to this variance in color, the light generated during these transitions, which are referred to as spoke times may not be employed.
In certain circumstances, however, a technique known as spoke light recovery (“SLR”) maybe employ to use light generated during spoke times. In particular, if the shade of the red light, green light, and blue light components of a pixel are each above a threshold LSB value (e.g., 150) the light generated during the spoke times can be employed. Although SLR can boost the light output for certain shades of light, this boost in light output can create a sudden increase in light output when a video display switches from a non-SLR shade to an SLR shade. Conventional SLR systems compensate for this boost in light output decreasing the non-spoke light by a fixed amount when SLR is employed. However, as light sources age, the amount of light that the light source generates may change, and a fixed compensation cannot adjust for these changes.
An improved method and system for spoke light compensation is desirable.